Spinal fixation devices can be used to provide, for example, immobilization and stabilization of spinal segments in patients (e.g., humans, dogs, cats, and other animals). Fixation devices may be used to help fuse bone segments (e.g., vertebrae) in the treatment of instabilities or deformities of, for example, the cervical, thoracic, lumbar, and/or sacral spine. Such instabilities or deformities may include, for example, degenerative disc disease (DDD); spondylolisthesis; trauma (i.e., fracture or dislocation); spinal stenosis; curvatures (i.e., scoliosis, kyphosis, and/or lordosis); tumor; pseudoarthrosis; and failed previous fusions.
FIGS. 1A, 1B, 1C, 1D, 1E depict a conventional spinal fixation system. FIG. 1A includes a fixation screw 101 located at the distal end of extension sleeve system, sometimes referred to as a “tulip”. More specifically, screw 101 is included in the “saddle” 107, which couples to sleeves 102, 103. The sleeves are separated from each other by windows 105, 106. There is a circular recess 108 near the distal end of the system. FIG. 1B shows the same system as FIG. 1A but without screw 101 deployed in the saddle 107. FIG. 1C shows a side view of the same system. FIG. 1D shows a 90 degree rotation from the perspective of FIG. 1C. FIG. 1E shoes a close up of the proximal end of the system of FIG. 1B. Screw 101 may be deployed through orifice 109, down between sleeves 102, 103, and into saddle 107 and bone (e.g., pedicle, femur, humerus) that connects to saddle 107. Screw 101 may be inserted using an implant device, such as a screw driver, that is also inserted into orifice 109 or windows 105, 106. The two arms 102, 103 collectively couple to one another via ring portions 110, 111 at the proximal end of the tulip.
In greater detail, a physician slides screw 101 through the orifice 109 and into saddle 107. In some instances the screw may already be located in the saddle when the physician receives the system. After the screw is implanted into bone the physician will remove and/or break the ring portions 110, 111. By breaking the ring portions the proximal arms or sleeves 102, 103 are no longer directly connected to one another at the proximal end of the system. Instead, sleeves 102, 103 only indirectly couple to one another via saddle 107. So by breaking the ring portions 110, 111 (e.g., at one location 115 above window 105 and at another location 116 above the other slot or window 106), the proximal portions of arms 102, 103 may be moved independently of each other. Now the physician may “work” or bend back and forth the two arms 102, 103. Doing so helps fatigue the system at the distal ring 108 so that the arms break off from the saddle 107 at distal ring 108, thereby leaving only the saddle and screw in the patient. The two arms 102, 103 from the tulip may be removed.